The blue graph shows the apparent percentage (not the absolute number) of marine animalgenera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized. The labels of the "Big Five" extinction events are clickable hyperlinks; see Extinction event for more details. (source and image info)

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At least half of the species now known to have been living on Earth at that time went extinct. This event vacated terrestrial ecological niches, allowing the dinosaurs to assume the dominant roles in the Jurassic period. This event happened in less than 10,000 years and occurred just before Pangaea started to break apart. In the area of Tübingen (Germany), a Triassic-Jurassic bonebed can be found, which is characteristic for this boundary.[4]

Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a decrease in speciation than by an increase in extinctions.[5]

Several explanations for this event have been suggested, but all have unanswered challenges:

Gradual climate change, sea-level fluctuations or a pulse of oceanic acidification[6] during the late Triassic reached a tipping point. However, this does not explain the suddenness of the extinctions in the marine realm.

Asteroid impact, but so far no impact crater of sufficient size has been dated to coincide with the Triassic–Jurassic boundary.

The eroded Rochechouart crater in France has most recently been dated to 201 ±2 million years ago,[7] but at 25 km across (possibly up to 50 km across originally), appears to be too small.[8] (The impact responsible for the annularManicouagan Reservoir occurred about 12 million years before the extinction event - the Rochechouart crater is now thought to have been caused by part of the same fragmented impactor.)

The isotopic composition of fossil soils of end Triassic and Early Jurassic has been tied to a large negative carbon isotope excursion (Whiteside et al. 2010). Carbon isotopes of lipids (n-alkanes) derived from leaf wax and lignin, and total organic carbon from two sections of lake sediments interbedded with the CAMP in eastern North America have shown carbon isotope excursions similar to those found in the mostly marine St. Audrie’s Bay section, Somerset, England; the correlation suggests that the end-Triassic extinction event began at the same time in marine and terrestrial environments, slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco (Also suggested by Deenen et al., 2010), with both a critical CO2 greenhouse and a marine biocalcification crisis.

Contemporaneous CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same places, making the case for a volcanic cause of a mass extinction. The catastrophic dissociation of gas hydrates (suggested as one possible cause of the largest mass extinction of all time, the so-called "Great Dying" at the end of the Permian Period) may have exacerbated greenhouse conditions.